Well, I just thought I would have to go back on myself....is there a way to get back and forth between T1 international and T3 international without going landside? Reason is that if I get bumped off the VS flight I can go back to T1 international to get the next BA one....
No you wouldn't be able to go back on yourself. You would have to go through connections security if you wanted to go to T1 Domestic
or T3 from T1 International.
T1I to T3 might be easier landside but you would have some difficulty getting landside from T1I departures. The easiest way through really would just be to follow FCC signs and clear security airside and take the connections route to T3.